1. Technical Field
The invention relates to an imaging apparatus equipped with a solid-state imaging device and an image signal processing method used in the imaging apparatus. Particularly, the invention relates to an imaging apparatus that can capture an image of a subject with a wide dynamic range and that can capture continuous two images (e.g. a flashed image and a non-flashed image) in one shooting operation, and an image signal processing method used in the imaging apparatus.
2. Related Art
A solid-state imaging device such as a CCD image sensor or a CMOS image sensor having at least millions of pixels mounted on one chip has become popular recently with the advance of increase in the number of pixels. For this reason, the quantity of signal charges allowed to be stored in each pixel has been reduced to a very small value in accordance with reduction in the size of each pixel, so that there is a tendency for an overexposed or underexposed image to be captured and for the dynamic range of a subject image to be narrowed.
In a digital camera described in JP 2001-275044 A (corresponding to U.S. Pat. No. 7,030,923), pixels are separated into a group of pixels to be exposed for a long time and a group of pixels to be exposed for a short time so that a composite image is generated by combining subject image data obtained by the long-time exposure and image data obtained subject image data obtained by the short-time exposure to thereby achieve enlargement of the dynamic range.
In a digital camera described in JP 2007-256907 A (corresponding to US 2007/0189753 A), two shooting operations (i.e. flashed image capturing and non-flashed image capturing) are performed continuously in one release operation in order to reduce the probability of failed image capturing.
JP 2001-275004 A does not consider timings at which flashlight should be emitted in the long-time exposure and the short-time exposure when it is required to capture a flashed subject image.
In JP 2007-256907 A, there is a time difference between the two kinds of shooting, so that there is a problem that image capturing may be failed because facial expression will become poor in spite of good brightness or brightness will become poor in spite of good facial expression if a main subject moves or facial expression changes in the time difference.